Adhesive bonding and miscellaneous chemical manufacture – Differential fluid etching apparatus – With microwave gas energizing means
Reexamination Certificate
1999-05-18
2001-05-22
Dang, Thi (Department: 1763)
Adhesive bonding and miscellaneous chemical manufacture
Differential fluid etching apparatus
With microwave gas energizing means
C118S7230ER, C118S725000, C118S728000
Reexamination Certificate
active
06235146
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a vacuum treatment system for treating an object, such as a wafer, using a plasma or the like, in a low pressure atmosphere, and to its stage. More particularly, the invention relates to a vacuum treatment system, which is suited to perform etching of a wafer or the like at a high temperature, and to its stage.
Regarding a system for treating an object, such as a wafer, using a plasma or the like, in a low pressure atmosphere, a conventional technique of electrostatically attracting a wafer to a stage using an electrostatic attracting means and treating the wafer with a plasma has been proposed in Japanese Patent Application Publication Nos. 56-53853 and
57-44747
. Unexamined Japanese Patent Application Publication Nos. 58-32410 and 60-115226 disclose a wafer treating method including the steps; of electrostatically attracting a wafer to a stage using an electrostatic attracting means, introducing an He gas to the back face of the wafer, and cooling or heating the wafer by thermal conduction, free convection, and forced convection.
In an ordinary etching process, the temperature at the wafer placing face of the stage is controlled to about 80° C. or lower. In some etching processes, however, controlling the wafer temperature to about 100 to 200° C. is needed. More specifically, in the etching of a multilayered film made of a metal and polysilicon, when a metal film is etched, the sample is treated at a high temperature of 100° C. or higher. Therefore, the etch rate of the metal film becomes high, so that excellent etching without causing a partial etch residue in the metal film and a barrier film can be realized. The barrier film is a film inserted between the metal and polysilicon in order to suppress inter diffusion. As a metal, tungsten can be used. As a material of the barrier film, tungsten nitride can be used.
A conventional ordinary stage for an etching process having an electrostatic attracting means is formed by thermal spraying of Ni and Al onto a base aluminium alloy and, then, by thermal spraying of alumina ceramics to form a dielectric film for electrostatic attraction. A stage support also serving as a linear guide shaft and a linear guide bearing are so provided under the stage as to vertically move the stage when a wafer is loaded/unloaded onto/from the placement face.
When it is assumed that a vacuum treatment system having a conventional stage is applied to a wafer treatment at a high temperature, there are the following problems.
First, in the conventional stage using aluminium as a base material, the coefficient of thermal expansion of aluminium as a base material is 24×10
−6
[°C.
−1
]. If the temperature is increased from room temperature to 160° C., the thermal strain is &egr;=24×10
−6
[°C.
−1
]×(160−25) [°C.]=3.2×10
−3
. At this time, a thermal strain is also introduced in the dielectric film for electrostatic attraction. The strain is obtained by &egr;1=7×10
−6
[°C.
−1
]×(160−25) [°C.]=0.95 ×10
−3
from the coefficient of thermal expansion of alumina ceramics of 7×10
−6
[°C.
−1
]. Since the Young's modulus of alumina ceramics is E=2.6×10
4
[(kgf/mm
2
], the thermal stress applied on the dielectric film at this temperature difference is obtained by &sgr;=(&egr;−&egr;1)×E=59 [kgf/mm
2
]. The stress is larger than 29 [kgf/mm
2
] of the strength of alumina ceramics. The alumina ceramics therefore become fractured and so electrostatic attraction cannot be employed.
Conventionally, the stage, the insulating plate, and the stage support are entirely in close contact with each other and have a structure such that heat escapes easily from the stage to the stage support. It is therefore difficult to maintain the wafer placement face of the stage at a high temperature. The tendency becomes more conspicuous as the amount of heat flow to the wafer increases and the diameter of the wafer becomes larger.
Further, conventionally, a linear guide bearing is positioned in the vacuum above a bellows. By using the stage support as a linear guide shaft, the stage is moved vertically without causing shaft runout. As the bearing, a solid bearing made of a fluororesin is employed. In the case of the conventional structure, when the stage is controlled at a high temperature, the temperature of the stage support serving as a guide increases due to the influence of the heat flow. In this case, there is a problem in that the clearance with the bearing becomes zero, the bearing functions as a brake, and the stage can not move vertically.
SUMMARY OF THE INVENTION
It is a first object of the invention to provide a stage with an electrostatic attracting means, which is adapted to wafer treatment at a high temperature, and a vacuum treatment system having the stage.
It is a second object of the invention to provide a stage, which can maintain the temperature of a wafer placement face at a predetermined high temperature, and a vacuum treatment system having the stage.
It is a third object of the invention to provide a stage, which can be moved smoothly in the vertical direction even when the temperature of the stage becomes high, and a vacuum treatment system having the stage.
In order to achieve the first object of the invention, there is provided a vacuum treatment system, having a stage provided in a treatment chamber, for electrostatically attracting an object to the stage in a low pressure atmosphere and treating the object at a high temperature by heating the stage, wherein an electrode member of the stage is made of titanium or a titanium alloy and a dielectric film for electrostatic attraction is formed on the electrode member.
Since the electrode member is made of titanium in accordance with the invention, even when the temperature of the stage becomes high, the thermal strain in the stage is small and the thermal stress can be suppressed so as to be smaller than the strength of the alumina ceramics.
Since the bonding between titanium and alumina ceramics is not firm, it is desirable to sandwich a nickel alloy (Ni—Al) between the materials.
In order to achieve the second object of the invention, there is provided a vacuum treatment system comprising: a stage provided in a treatment chamber and held by a stage support; a means for heating an electrode member of the stage; and an insulating plate provided between the electrode member of the stage and the stage support, for electrostatically attracting an object to the stage in a low pressure atmosphere and treating, the object at a high temperature by heating the stage wherein the electrode of the stage is made of titanium or a titanium alloy, a clearance for thermal insulation is provided between the electrode member and the insulating plate, and a clearance for thermal insulation is provided between the insulting plate and the stage support.
In accordance with the invention, a structure in which clearances are provided respectively between the stage and the insulating plate and between the insulating plate and the stage support is adopted. When a sample is treated, the pressure around the stage is about 1 Pa and the structure is effective as a vacuum insulation. That is, a stage which can efficiently transfer heat by reducing the heat flow escaping from the stage to the stage support is provided.
In order to achieve the third object of the invention, there is provided a vacuum treatment system comprising: a stage provided in a treatment chamber and which is held movable in the vertical direction by a stage support via a bearing; a means for heating an electrode member of the stage; and an insulating plate disposed between the electrode member and the stage support, for electrostatically attracting an object to the stage in a low pressure atmosphere, and treating the object at a high te
Fujii Takashi
Hamasaki Ryouji
Itou Youichi
Kadotani Masanori
Kanai Saburo
Antonelli Terry Stout & Kraus LLP
Dang Thi
Hitachi , Ltd.
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